Throughout the world, many systems, such as, for example, power generation plants, which depend upon an inflow of a heated or super-heated working fluid (e.g., steam or a chemical refrigerant) to turn mechanical energy into electrical energy, produce exhaust gases that are usually extremely hot. These gases are often exhausted into the open atmosphere, thereby wasting any residual heat energy contained therein. Since the operation of such systems depends upon the inflow of a heated or super-heated fluid, the overall efficiency of these systems may be improved by a mechanism, such as, for example, a heat exchanger, configured to recapture at least a portion of the residual waste heat energy for use in heating the incoming working fluid.
In those systems that use a chemical as the working fluid, such as, for example, an organic Rankine cycle, the working fluid may be piped through a first tube, while the exhaust gases are piped through a second tube that concentrically surrounds the first tube, in order to efficiently transfer heat energy from the exhaust gases to the working fluid. In such an arrangement, since the exhaust gases are usually extremely hot, the surface temperatures of the first and second tubes can frequently exceed the fluid degradation temperature of the chemical working fluid, thereby causing any molecules of the chemical working fluid in direct contact with a surface of the first tube to overheat and breakdown or disintegrate.
Working fluid degradation has been addressed in the art by utilizing an intermediate fluid, such as, for example, water, to aid in the transfer of heat energy from the hot exhaust gases to the chemical working fluid. For instance, the use of such an intermediate fluid is described in U.S. Pat. No. 6,571,548 issued to Bronicki et al. on Jun. 3, 2003. Although such use of an intermediate fluid appears viable, the high expense, complexity, and loss of heat energy involved with a separate intermediate fluid heat transfer mechanism renders it commercially challenged. Providing a mechanism to efficiently utilize a maximum amount of waste heat energy contained in exhaust gases, while minimizing working fluid degradation without having to reduce the overall working fluid temperature or sacrifice efficiency, has therefore been problematic and elusive.
The present disclosure is directed to overcoming one or more of the shortcomings set forth above.